红花芸豆色素的提取及稳定性研究

本研究探讨了红花芸豆色素的最佳提取条件和色素的稳定性。实验表明最佳的提取工艺为:料液比1:75,提取温度60℃,提取时间90min。红花芸豆色素光、热稳定性好;在酸性条件下稳定,当pH≥4时出现混浊;对糖有一定稳定性;山梨酸钾、苯甲酸钠、柠檬酸对色素无不良影响;VC和H2O2对色素的稳定性有影响,色素对低浓度的VC较稳定。金属离子Na+、K+、Ca2+对色素无影响,而Fe3+、Cu2+、Fe2+、Zn2+、Mg2+对色素有明显影响。     

氯化钠与碳酸氢钠对牛肉食用品质的影响

试验旨在研究不同浓度的氯化钠(Na Cl)和碳酸氢钠(Na HCO3)对牛肉品质的影响。以新鲜黄牛腿肉为材料,共7组(每组3重复),分别取150g左右的肉样,再以肉样10%的比例分别均匀注入10%Na Cl(第1组)、9%Na Cl+1%Na HCO3(第2组)、8%Na Cl+2%Na HCO3(第3组)、7%Na Cl+3%Na HCO3(第4组)、6%Na Cl+4%Na HCO3(第5组)、5%Na Cl+5%Na HCO3(第6组)、蒸馏水(对照组)。置于4℃冰箱内,观察腌制1、3、5、7d后,p H值、剪切值、失水率、熟肉率的变化。结果表明:氯化钠和碳酸氢钠组合提高p H值,明显减小剪切力,增加嫩度,降低失水率,提高熟肉率;同时5%Na Cl+5%Na HCO3组合效果最佳。本研究结果可知,添加碳酸氢钠溶液可以在一定程度上改善牛肉的食用品质。     

基于应力松弛原理的高酰基结冷胶凝胶特性研究

本文采用应力松弛模式研究了一价离子(K+和Na+)和二价离子(Ca2+和Mg2+)对高酰基结冷胶凝胶特性的影响。结果表明:高酰基结冷胶凝胶的应力松弛行为符合Peleg经验模型。离子浓度和离子种类对高酰基结冷胶凝胶应力松弛行为影响显著,平衡弹性模量(EA)随着离子浓度的增加呈马鞍形趋势变化,且其与凝胶硬度呈现较好的正相关(R=0.943~0.983),表明EA可以用来表征高酰基结冷胶凝胶的强度。相对于一价离子(K+、Na+)而言,二价离子(Ca2+、Mg2+)形成的凝胶强度更高,且用量更少。在相同离子浓度下,Na+形成的凝胶比K+形成的凝胶强,Ca2+形成的凝胶则比Mg2+形成的凝胶强。在16000 g下离心10 min,高酰基结冷胶凝胶保水性均在95%以上,与离子浓度基本无关,保水性能优异。高酰基结冷胶应力松弛机制是体系内部物理交联点的移动。     

非靶向快速筛查茶饮料中未知农药残留

本文建立了分散液液微萃取-高效液相色谱-四极杆-飞行时间质谱法(DLLME/HPLC-Q-TOF/MS)非靶向快速筛查茶饮料中未知农药残留的方法。根据目标化合物特征离子的精确质量数、同位素匹配、二级碎片信息进行数据库匹配,筛查可疑未知农药。依据13种农药为质控化合物优化了测定方法。结果表明,2 g N-丙基乙二胺为预净化剂,甲醇为分散剂,200 μL三氯甲烷为萃取剂,通过摇床震荡的方式提取茶饮料中的目标化合物,Xbridge BEH C18色谱柱分离的方法回收率范围为83.1%~96.8%,RSD范围在0.88%~4.82%。空白基质校准曲线的线性范围为2~400 μg/L,决定系数R2在0.9989以上,检测限为0.002~0.092 μg/kg,定量限为0.006~0.307 μg/kg。该方法无需标准品即可快速筛查茶饮料中的农药残留,能够应用于茶饮料样品的实际筛查。该方法快速、准确、分析通量高,可以为茶饮料中农药残留的快速筛查和质量控制提供重要的方法依据。     

高产蛋白酶根霉菌株的筛选及酶学性质研究

试验以实验室保存的12株根霉菌为研究对象,通过平板初筛、发酵复筛筛选出产蛋白酶活力强的菌株,并对其蛋白酶的最适反应温度、最适p H值以及金属离子对酶活力影响等酶学性质进行研究。平板初筛中选出了R8、R9和R12三株HC值大的菌株进一步复筛。发酵复筛中测定三株菌的蛋白酶活力依次为R8>R9>R12。进一步对三株菌的蛋白酶性质进行研究,结果表明,几株菌所产蛋白酶的最适温度都在40℃左右,p H值对三株菌蛋白酶活力影响较大,R8和R9在p H5.5~6.0酶活力强,R12在p H6.0~6.5酶活力强。K+、Ca2+、Mg2+对酶促反应有一定促进作用,Cu2+、Zn2+对酶促反应有抑制作用,Na+对酶促反应的影响不大。     

高效液相色谱-四极杆飞行时间质谱技术非靶向快速筛查荔枝花、蜂巢和蜂蜜中农药

利用高效液相色谱-四极杆飞行时间质谱结合QuEChERS前处理技术,建立荔枝花、蜂巢和蜂蜜中未知农药残留的非靶向快速筛查方法。样品均由乙腈溶液提取,经无水硫酸镁、N-丙基乙二胺和十八烷基键合硅胶吸附剂净化,采用Xbridge BEH C18色谱柱分离,以甲酸溶液-乙腈为流动相进行梯度洗脱,在电喷雾离子源、化学电离源和正反监测模式条件下进行检测。利用目标化合物特征离子的精确质量数、同位素匹配、二级碎片信息和保留时间进行数据库匹配,筛查可疑未知农药,在Targeted MS/MS模式下,通过相应碰撞能量下的离子碎片信息进一步确证,以基质匹配标准溶液法定量。结果显示：共计筛选出嘧菌酯、吡唑醚菌酯及其代谢物BF 500-3、苯醚甲环唑、多菌灵、毒死蜱、除虫脲和灭幼脲8 种农药,在1～1 000 μg/L范围内线性关系良好,相关系数r2均大于0.99,方法的检出限为0.03～0.50 μg/kg,定量限为0.4～0.8 μg/kg。8 种农药在荔枝花、蜂巢和蜂蜜中的平均加标回收率为80%～96%,相对标准偏差为1.2%～6.1%。该法快速、简便、灵敏,可用于荔枝花、蜂巢和蜂蜜样品中未知农药的筛查和鉴定。     

高良姜色素提取方法筛选及其性质研究

为开发利用我国南方特产高良姜及其色素,筛选出发酵酸解法提取了高良姜色素。扫描出高良姜色素的紫外吸收光谱,得到其最大吸收波长λmax=325nm。测定其折光率为1．361。初步探讨其提取机理。试验了该色素的溶解性和光、热、pH值、Na2SO3、H2O2、常用七种食品添加剂、Fe3+、Cu2+、Zn2+、Na+对色素稳定性的影响。结果表明:高良姜色素在pH2～5、光照、Fe3+、Cu2+、Zn2+、Na+、Na2SO3、七种常用食品添加剂的作用下稳定,但遇H2O2或受热则易褪色。该色素具有开发利用价值。     

黄酒中丁二酸的分离、纯化和鉴定

采用AB-8大孔树脂和反相C18柱色谱分离获得了黄酒中的1个较强极性的物质,经红外光谱显示该物质含有C=O键和C-O键,并有-CH2-存在;核磁共振谱图显示含有-COOH和-CH2-基团,其比例为1:1;GC-MS证实了该物质的纯度较高,基峰质荷比为55,M+1峰的质荷比为119,含有COOH+(m/z=45)和亚稳态离子峰C2H3+(m/z=27)的碎片,综合解析后推断该物质为丁二酸,为黄酒酿造过程中微生物发酵所产生,对黄酒的风味和功能都具有重要影响.     

“南盐一号”库拉索芦荟对海水胁迫的响应

考察了4组库拉索芦荟(F0CK、F50CK、F060%、F5060%)叶片的鲜重、干重,叶片内Na+、K+、Mg2+、Ca2+离子的含量以及质膜透性,丙二醛含量。结果表明:同在60%海水(即海水∶淡水体积比3∶2)胁迫下,F5060%的干湿重比远大于F060%的干湿重比;F5060%叶片内的Na+离子含量显著小于常规芦荟,K+离子含量远高于常规芦荟,F5060%芦荟较F060%拥有更高的K+/Na+和更低的Na+/Ca++;芦荟叶片的质膜透性显著上升,丙二醛含量也有小幅度上升,但F50上升幅度都较F0小。可见,F50库拉索芦荟较F0库拉索芦荟在抗海水胁迫能力上有一定程度的提高。     

高酰基结冷胶与κ-卡拉胶复配胶的质构特性研究

用抗压实验和全质构测试对高酰基结冷胶(HA)与κ-卡拉胶(CA)复配胶的凝胶强度、形变性以及硬度进行分析。研究了Ca2+、Mg2+、K+、Na+四种离子以及HA与CA的质量比对复配胶质构特性的影响。实验中,总胶浓度控制为1%(w/v),离子浓度为2～80mmol/L,HA和CA的质量比为25:75、50:50、75:25。结果表明,二价离子较一价离子作用效果显著,其中Ca2+效果最为显著,复配胶在HA:CA=75:25时有显著的协同作用,HA与CA的复配胶有着较强的形变性。     

自动QuEChERS结合液相色谱-串联质谱法测定香叶中的212种农药残留

目的 建立自动QuEChERS结合液相色谱-三重四极杆串联质谱法测定香叶中212种农药残留。方法 香叶样品用乙腈提取,使用300 mg十八烷基硅烷键合硅胶(C₁₈)+75 mg Nano-Carb、4.0 g无水硫酸镁和1.0g氯化钠进行净化,经自动样品制备系统进行制备后,应用液相色谱-三重四极杆串联质谱法进行检测,在电喷雾电离正离子模式下扫描,动态多反应监测(dynamic multiple reaction monitoring, DMRM)模式下检测,基质匹配外标法定量分析。结果 212种目标农药在各自线性范围内线性关系良好,线性相关系数(γ²)均大于0.995,检出限(limits of detection, LODs)范围为1-5μg/kg,定量限(limits of quantitation, LOQs)范围为2-20μg/kg,在10、50和100μg/kg的添加水平,212种农药的平均回收率范围分别为70.35%-112.49%、70.30%-107.02%和72.39%-95.87%,相对标准偏差均小于14.1%。结论 该方法快速、准确、灵敏度高,能够应用于香叶中多农药残留的高通量定性筛查和准确定量,并可扩展到其他香辛料多农药残留检测中。     

Identification of New Coloured Anthocyanin–Flavanol Adducts in Pressure-Extracted Pomegranate (<Emphasis Type="BoldItalic">Punica granatum</Emphasis> L.) Juice by High-Performance Liquid Chromatography/Electrospray Ionization Mass Spectrometry

Pomegranate (Punica granatum L.) juice, obtained by pressure extraction of the whole fruit, contains coloured flavanol–anthocyanin adducts (the flavanol occupies the upper part of the dimmer) from the direct condensation between anthocyanidins delphinidin, cyanidin and pelargonidin and flavan-3-ols (epi)gallocatechin, (epi)catechin and (epi)afzelechin. The presence of adducts between these same flavanols and anthocyanidins, but belonging to the coloured anthocyanin–flavanol adduct type (anthocyanin occupies the upper part of the dimmer) has been revealed by reversed-phase liquid chromatography coupled to tandem mass spectrometry (ion trap), with positive electrospray ionization (LC–ESI/MS ⁿ ). These new adducts are isotopic with their corresponding counterparts (flavanol–anthocyanin adducts) and indistinguishable from them by comparison of the mass spectra from the MS² of the isotopic parent ions. However, they can be distinguished by comparison of the mass spectra from the MS³ of their corresponding isotopic aglycons. Hence, the MS³ of the aglycon from a given flavanol–anthocyanin adduct always yields a mass spectrum containing five characteristic ions, the three with smaller m/z being only dependent on the anthocyanidin and the other two on both the anthocyanidin and the flavanol. In contrast, the mass spectrum from the MS³ of the aglycon of its counterpart anthocyanin–flavanol adduct gives only two of the above five characteristic ions, where the ion with smaller m/z only depends on the anthocyanidin and the other on both the anthocyanidin and the flavanol. Ten 3-hexoside derivatives of coloured anthocyanin–flavanol adducts were detected in pomegranate juice being reported for the first time this type of adducts from a natural source.     

Formation of protein adducts of 2‐amino‐1‐methyl‐6‐phenylimidazo[4,5‐b]pyridine in cooked foods

Heterocyclic amines (HCAs) are mutagenic and carcinogenic compounds found in cooked meat and fish. Although HCAs are known to form adducts with protein after metabolic activation, adduct formation during cooking has not been elucidated. In this study, we showed that 2‐amino‐1‐methyl‐6‐phenylimidazo[4,5‐b]pyridine (PhIP) is released from high molecular weight compounds by acid or enzymatic hydrolysis of cooked foods. Formation of free and protein adduct forms of PhIP was dependent on cooking temperature and time, and PhIP–protein adducts were estimated to form after formation of free PhIP. We also demonstrated that PhIP–protein adduct is formed by heating of PhIP and albumin as a model protein. A new adduct peak including [M+H]⁺ (m/z=225) of PhIP as a fragment ion was detected in the high molecular weight fraction of heat‐treated protein by LC–MS analysis. From model experiments by heating of PhIP and amino acids, the adduct was estimated to be produced by condensation of the amino group of PhIP and the carboxyl group of protein. PhIP–protein adducts were detected in several cooked meat and fish at ng/g food level as PhIP content. These results suggest that food‐borne protein adducts of HCAs may influence human HCA exposure and carcinogenic risk.     

Relative importance of charge neutralization and precipitation on coagulation of Kaolin with PACI: effect of sulfate ion

The effect of the sulfate ion on coagulation with polyaluminum chloride (PACl) was investigated by using an optical monitoring technique together with the conventional jar test procedure and electrophoretic mobility (EM) measurements. The effect of the SO4(2-)/Al ratio, dosage, and pH were examined in detail. The experimental results show that sulfate has a significantly different effect on PACl coagulation as a result of preformed hydrolysis products, where charge neutralization and precipitation play different parts in the coagulation process. The increased rate of coagulation with increasing SO4(2-)/Al ratio can be partially explained by charge neutralization effects, through increased adsorption and complexation of sulfate, thus giving increased particle collision efficiency. Different PACl samples were prepared with different values of B ([OH]/[Al]). For B = 0 (i.e., AlCl3) with mainly monomers, hydroxide precipitation tends to be accelerated in the presence of sulfate, giving significant turbidity removal. The high charge neutralization ability remains for samples with B = 1.5 and 2.0, with large proportions of preformed oligomers and polymers. Sulfate promotes aggregation of hydrolyzed species for B= 2.5, causing significantly improved coagulation efficiency through an electrostatic patch effect. The results illustrate further that particle charge plays a less important role in coagulation after reaching a certain value, while precipitate formation improves coagulation significantly.     

超高压液相色谱-高分辨质谱法同时筛查蓝莓中90种农药残留

建立了超高压液相色谱-高分辨质谱同时筛查蓝莓中90种农药残留的方法。采用改良的QuEChERS方法提取目标物残留,超高压液相色谱-四极杆/离子回旋轨道阱高分辨质谱正负离子模式全扫描-数据依赖性碎片离子采集,代表性基质匹配标准工作曲线定量。结果显示:改良的QuEChERS净化填料中,PSA和C₁₈净化粉的用量均在150 mg时净化效果最好;方法检出限和定量限分别为0.1～18.7 μg/kg和0.2～20.2 μg/kg,90种农药在0.005～0.1 mg/kg范围内,线性关系良好,决定系数R2≥0.992;在0.01、0.05和0.1 mg/kg浓度水平进行基质添加回收实验,回收率50.1%~130.9%,相对标准偏差为1.0%～14.9%。在对实际样品的筛查中,检测到5种农药残留显示了方法的实际应用效能。本方法前处理简便、目标分析物覆盖范围广、在筛查定量基础上可同时完成高精度定性分析,可有效用于蓝莓中常用农药残留的监测。     

Screening method for the determination of 199 pesticides in agricultural products by gas chromatography/ion trap mass spectrometry (GC/MS/MS)

A screening method is described for determining 200 pesticides, except dimethipin, divided into four groups by means of gas chromatography/tandem mass spectrometry (GC/MS/MS) using an ion trap mass spectrometer equipped with automated gain control (AGC). The quantitation limit for 194 pesticides was 0.01 mg/kg on a crop basis, except for allidochlor, dimethoate, hexythiazox, methamidophos and triadimenol. The calibration curve of each pesticide was linear in the range of 0.04-5.0 microg/mL. One hundred and ninety-nine pesticides were added to matrix of potato, spinach, cabbage, apple, orange, soybean and unpolished rice at twice the limits of quantitation. The recoveries of 194 pesticides from all crops were satisfactory (50-150%) for screening purposes. Although some pesticides in apple and orange were not determined by selected ion monitoring (SIM) analysis at the limits of quantitation, all of them were identified by ion-trap GC/MS/MS at the same concentration. Thus, the ion trap GC/MS/MS technique is useful for the screening of residual pesticides present at low levels in agricultural products.     

Multi-residue method for screening of pesticides in crops by liquid chromatography with tandem mass spectrometry

A simple and rapid method was developed for the screening of 82 pesticides/metabolites in a wide variety of crops, using solid-phase extraction and liquid chromatography with tandem mass spectrometry (LC/MS/MS). After extraction with methanol, the filtered extracts were made up to 100 mL and a 2 mL aliquot was subjected to solid-phase extraction. Co-extractives were removed with a C18 mini-column, while pesticides were retained on 3 kinds of mini-columns (HLB, SAX, activated carbon), and then eluted with acetonitrile. Analysis was performed by LC/MS/MS, and MS acquisition parameters were established in positive and negative ESI modes. The utility of the method was demonstrated by the analysis of 6 crops (carrot, cabbage, onion, spinach, lemon, brown rice) and one mixed vegetable juice. Of 82 compounds tested, 75 in carrot and 62 in lemon were obtained with recoveries ranging from 70-120%. For all samples tested, 75 compounds could be obtained with recoveries of over 50%, and the detection limits of most compounds were lower than 0.01 microg/g. This method provides acceptable performance for analysis of these 75 compounds. Further, by using aliquots of the extracts with small-scale mini-columns, purified samples could be obtained. This proposed method with small matrix effects, is effective and suitable for screening of multiple residual pesticides by using LC/MS/MS.     

丙烯醛-丙氨酸加合物制备与细胞毒性

丙烯醛是热加工食品中存在的有害物质,形成后易与氨基酸反应生成加合物,但目前对其加合物的毒性研究较少。本研究设置不同丙烯醛与丙氨酸浓度比（2∶1、1∶1、1∶2、1∶3、1∶4）,于37 ℃和50 ℃下分别水浴反应0.5、3、5、6 h,发现丙烯醛与丙氨酸浓度比1∶2在50 ℃反应5 h所获得目标加合物产率最高。通过反相硅胶柱层析进行分离纯化后,经高效液相和液相色谱-质谱联用分析,结果显示该加合物最大吸收波长为220 nm,纯度达95%以上。高分辨质谱和核磁共振鉴定结果表明,该加合物相对分子质量为183.082 3,是由一分子丙氨酸与两分子丙烯醛发生迈克尔加成反应后,经羟醛缩合形成的含氮六元环化合物。采用加合物培养人正常胃黏膜细胞（GES-1）24 h和48 h后发现,加合物半抑制浓度（half maximal inhibitory concentration,IC50）分别为3.286、0.869 mmol/L,显著降低了丙烯醛（IC50分别为0.058、0.067 mmol/L）的细胞毒性,说明丙氨酸可作为食品中丙烯醛的潜在清除剂。     

Internal exposure, health effects, and cancer risk of humans exposed to chloronitrobenzene

Chloronitrobenzenes (CNBs) are important intermediates for the production of dyes, pesticides, rubber chemicals, and drugs. 2CNB and 4CNB are possible human carcinogens. Therefore, it is important to develop methods to biomonitor people exposed to these occupational and environmental pollutants. We developed a method to determine hemoglobin (Hb) adducts of CNBs. Nitrobenzenes and the resulting arylamines yield the same sulfinamide adducts. Therefore, after base hydrolysis of the isolated Hb the corresponding arylamines are released and quantified by GC-MS. The method was applied to monitor 39 Chinese workers exposed to CNB and 15 control workers from the same factory. The determined Hb adduct levels were compared to the measured air levels, the clinical blood and urine parameters, and health effects identified in the workers. The median Hb adduct levels resulting from exposure to 2CNB and 4CNB were 82.9 and 1013 pg/mg of Hb, respectively. The median air concentrations determined from personal samplers were 0.37 and 0.87 mg/m3 for 2CNB and 4CNB, respectively. The air levels did not correlate with the Hb adduct levels. The median Hb adduct levels were higher in workers with fatigue, eye irritation, splenomegaly, and cardiovascular effects. Most negative urinary clinical parameters were present at higher median Hb adduct levels. The clinical blood parameters decreased at higher adduct levels. The daily dose was estimated from the Hb adduct levels and used to estimate the cancer risk.     

QuEChERS-UPLC-MS/MS法同时测定刺梨中11 种农药残留

目的：建立高维生素含量刺梨果实中11 种常用农药残留量的测定方法。方法：采用添加回收实验筛选和优化QuEChERS前处理方法的提取剂和净化方式,最终选用乙腈提取,N-丙基乙二胺和石墨化碳黑进行净化,以0.1%甲酸溶液和乙腈为流动相,用0.4 mL/min的流速梯度洗脱;在电喷雾正离子模式下,通过优化各农药离子对的碎裂电压、碰撞能量,以获得最佳响应,采用基质加标准曲线进行定量。结果：经方法验证,11 种农药的方法检出限在1.31～8.56 μg/kg之间,定量限在4.13～43.57 μg/kg之间,线性相关系数（R）在0.991 2～0.999 9之间;方法选择3 个添加水平进行添加回收率实验,回收率在84.5%～103.8%之间,相对标准偏差（n=6）在1.2%～8.5%之间。结论：该方法前处理快速、灵敏、准确,可为刺梨中农药的监管提供技术支持。